CDU [Capacitor Discharge Unit] ;

[Artificer]

CDU [Capacitor Discharge Unit] ;

I am considering purchasing the above to assist the movement of a  surface mounted point motor. 

Can a CDU be used in line with a hornby DCC accessory decoder [R8247] & a hornby select digital controller [R8213]. ? if so is what CDU would be appropriate?

[Rog RJ]

No, you cannot use a CDU with Hornby accessory decoders, in fact, they have one built in!

[Chrissaf]

As Rog says you cannot use a CDU [DIRECTLY] with a R8247, it won't work and to try, risks damaging the R8247. However, if you use the output of the R8247 to operate a 12 volt coil relay with a make contact (two relays per port required on the R8247), then use the relay contact to operate the point via an external CDU with its own separate power supply, then that will work. In fact that is exactly what I do to overcome the weak CDU function contained internally within the R8247.

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To be honest, this is only financially worthwhile if you have already spent money on R8247s and find that they are not powerful enough. The relays, CDU and separate power supply add a fair amount of cost per point. If you haven't yet purchased the R8247s, then there are other accessory decoder brand / models that have more power than the R8247. My point motors are PECO PL-10WE by the way.

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You shouldn't need an external CDU to supplement the R8247 if using Hornby motors, you do however need 100% perfect installation alignment to overcome drag. And if using R8243 surface mounted motors, do not have the fixing screws too tight, they need to be loose to prevent the point motor sticking. This (over tight fixing screws) issue with the Hornby R8243 motor is well documented on the forum

[Artificer]

Thank you for your response , I will only go down the relay/ cdu solution suggested as a last resort if I cannot resolve. Can I ask what relays and cdu, and the supplier u used as you appear to have had experience in this matter and a working solution.

Regards

Robert

[mallone]

Hi...if it's any help to you, I purchased an extra heavy duty CDU from jonblissett on eBay, a superb piece of kit. I power this with a 16vac power supply. It really does fire the points positively.

john.

[Artificer]

Thanks for the information on the cdu, can throw some light on the relays? Type / supplier and part no. 

Thanks again

robert

[96RAF]

Look on my linked web site in my signature at the wiring diagrams menu and you will see one for using a cdu with dcc. The relays were ordinary car headlight flasher type but you could use solid state electronics in lieu. The cdu was Gaugemaster and can fire up to 6 points at a time if memory of the data sheet is correct.

 

I need to repost a better wiring diagram than that one as some of the red lines are fading. In essence the dcc accessory decoder fires into the relay coil which discharges the CDU into the selected point solenoid or you can fire them by hand using any analogue switching method.

 

I have posted the picture previously on here but can't repost as this website is still playing up.

Rob

[Chrissaf]

Arti, could I kindly request for you not to use the "white arrow blue button" quote function, then NOT add any reply within the quote. The blue button is not a "Reply to this post" button. The best method to reply is the other method you are already using which is to use the "Reply text box" and the green "Reply" button.

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If you just want to indicate who's post you are referring to, just put their forum user name at the beginning of your text preceded by a @ such as for example "@Chrissaf". It really isn't necessary to keep duplicating previous posters replies.

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In answer to your question. I made my own mains powered CDU and manufactured my own relay PCB board. I do have full constructional documentation of how I made them and what components I used, but whilst the forum still has the 'image posting bug' present I am unable to post this information in these pages. The relays I used are PCB (copper strip board) mounted and have a pin pitch that is compatible with standard 0.1" copper strip board (be aware that not all PCB mounted relays have this 0.1" [2.54mm / 5mm] pin pitch).

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The relays I used have now been discontinued, but for reference they were Rapid-on-line Part Number 60-1274

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